they will both look good and last a long time on the bench.lol its a fad, dont know who started it but im sure it was an effort to reduce weight. the os speed comes in both now. and no mag has less memory than alum. at the nats no one was running the mag heads, cant get the rpms out of the motor on warm days with a poor cooling head. os had the same problem when they came out with the cv 12 that had a red square head but as soon as you put a better cooling head on it like the odonnell it was fast. i had the mr tuned motors at the nats and we put the alum head on. in cooler temps this head will work in fact ira runs onroad and perfers the mag head. so i guess the higher speeds keep the motor cool.